This invention pertains to an improved heat sensing apparatus for use with an automatic surface unit control for an electric range. In particular, it relates to heat sensing apparatus that electrically isolates the heat responsive sensor from the cooking utensil contact button while at the same time offering excellent thermal coupling with the cooking utensil. Such apparatus provides fast response times that make the apparatus of the invention particularly useful in combination with electronic range temperature controls.
The use of automatic temperature controls for electric range surface cooking units is old and well known. Typical examples are illustrated in U.S. Pat. Nos. 2,764,665 and 2,806,122. Generally a utensil temperature sensing device is mounted in the center of the cooking unit to come in physical contact with the bottom of the cooking utensil. Variations in the temperature of the utensil are sensed by a thermistor or a thermocouple arrangement and the resulting signal is used by the automatic temperature control circuitry in conventional manner to maintain a desired cooking temperature as set by the cook. Obviously, the ability of the sensor to accurately sense and follow the temperature variations in the cooking utensil is critical to the success with which the desired cooking temperature can be maintained.
The actual sensor, i.e. the thermistor or thermocouple, is usually mounted within a capsule or housing which is then supported by appropriate means in the center of the surface cooking unit. The interposition of a cover or cap on the housing between the utensil and the sensing device introduces time delays in the feedback loop that can result in significant, undesirable temperature variations occuring within the cooking utensil. Also, the placement of the sensor unit in the middle of the surface unit can result in the accuracy of the unit being adversely affected, both by the radiated heat from the heater coils and by heat transmitted through the support means and housing. In the past, these problems have been resolved by use of thin metal housings and appropriate shielding so that the inaccuracies were minimized to a level that worked satisfactorily with range surface unit controls then in existence.
However, it is now considered desirable to provide heat sensing apparatus with greater sensitivity to utensil temperature and faster response times particularly as electronic controls and improved fast response heating coils become more widely used.
It is, therefore, an object of the present invention to provide an improved heat sensing apparatus for an electric range automatic surface unit temperature control.
It is a further object of the invention to provide such heat sensor with fast response times suitable for use with electronic surface unit controls.
It is a still further object of the invention to provide heat sensing apparatus that is improved in sensitivity and response time over known devices and which is both simple and inexpensive in construction.